Aluminum dross is a combination of aluminum metal and aluminum oxides, as well as other possible components such as various oxides, nitrates and carbides. Aluminum dross constitutes a by-product of an aluminum melting operation. Generally, the dross floats on the top of the molten aluminum metal in the furnace. Aluminum dross may contain anywhere from ten (10%) to ninety (90%) percent aluminum depending upon the particular processing technique and the type of furnace. Dross, therefore, in an aluminum melting operation includes a significant amount of aluminum metal which is considered a valuable resource to be recovered. The recovery of aluminum from aluminum dross must also address the problem of the loss of aluminum metal in the dross due to thermiting or thermite reaction, i.e., exothermic oxidation of aluminum metal. It has been estimated that typically two (2%) percent of the aluminum metal is lost for each minute of cooling in at least some prior art systems. The present invention is directed at maximizing the recovery of aluminum from dross, and the present invention may be useful in recovering other non-ferrous metals from other drosses.
Various work has been done in the past on dross recovery systems for aluminum melting including work disclosed in U.S. Pat. Nos. 4,529,779--Roth, et al. and 4,386,956--Roth, et al., of which I am one of the joint inventors named in the foregoing cited patents. In these previous patents, there is some discussion of efforts that have been made prior to the filing dates of the applications which matured into those patents as well as discussion of some of the problems involved in the technology and other prior art dross recovery methods and systems. The teachings of the two foregoing Roth, et al. patents are incorporated herein by reference the same as if set forth at length.
Basically, the Roth, et al. patents disclose a process and apparatus in which compression is applied to aluminum dross placed in a trough receptacle by a wedge shaped compression head.